The present invention relates to a valve arrangement for a cylinder of an internal combustion engine arrangement. The invention is applicable for vehicles, in particularly heavy vehicles, such as e.g. trucks. However, although the invention will mainly be described in relation to a truck, the valve arrangement is of course also applicable for other type of vehicles, such as cars, industrial construction machines, wheel loaders, etc.
For many years, the demand on internal combustion engines have been steadily increasing and engines are continuously developed to meet the various demands from the market. Reduction of exhaust gas, increasing engine efficiency, i.e. reduced fuel consumption, and lower noise level from the engines are some of the criteria that becomes an important aspect when choosing vehicle engine.
In order to meet the described demands, various engine concepts have been developed throughout the years where conventional power cylinders have been combined with e.g., a pre-compression stage and/or an expansion stage. Such a cylinder arrangement is often called a two-stage engine, or a dual-stage engine.
A problem with a two-stage engine is that they are too over-expanded at low loads, which means that there is too much intercooled air, or other type of gas, added to the combustion cylinder, which results in that the over-expansion reaches sub atmospheric pressure. Hereby, the efficiency of the cylinder arrangement reduced since sub atmospheric pressure will create energy losses. Also, it is a problem that a lot of air needs to be pumped at low loads, which thus further tends to increase the energy losses of the cylinder arrangement.
EP 1 522 690 relates to a method of operating an internal combustion engine. According to an embodiment, an auxiliary valve is arranged to automatically prevent charge-air back flow from the cylinder.
US 2007/0204814 describes a split-cycle engine with disc valve assembly having a disc valve inlet which is an annular ring disposed between the engine block and the cylinder head.
There is hence a need to be able to control the intake of gas into a cylinder.
It is desirable to provide a valve arrangement which can control the amount of gas being provided into a cylinder of an internal combustion engine arrangement.
According to a first aspect of the present invention there is provided a valve arrangement for a cylinder of an internal combustion engine arrangement, the valve arrangement comprising a check valve configured to be positioned at an intake side port of the cylinder for controlling gas flow into the cylinder, wherein the valve arrangement further comprises an intake valve means positioned upstream from the check valve, and an actuating means configured to controllably position the intake valve means for closing the intake side port.
The wording “check valve” should in the following and throughout the entire description be interpreted as a valve which allows gas or fluid to pass through it in one direction only and thus preventing gas/liquid to flow through it in the other direction. Accordingly, for the above check valve which is configured to be positioned at an intake side port of a cylinder, gas can only flow into the cylinder via the check valve, and not out from the intake side port. A number of different check valves are available, such as a ball check valve, a diaphragm check valve, or a reed valve which will be described further below.
Moreover, the wording “intake valve means” should in the following and throughout the entire description be interpreted as a further valve configured to be positioned at the intake side port of the cylinder. Various types of valves are of course conceivable, and will be described in further detail below.
Furthermore, the “actuating means” should be understood as an arrangement which is configured to position the intake valve means in a closed position. Hence, the actuating means is configured to position the intake valve means in a position such that the intake side port is closed and thus preventing gas from entering the cylinder. Further, and as will be described below, the actuating means may only need to controllably position the intake valve means in a closed position. When the intake valve means is in a position such that the intake side port is closed, the actuating means may no longer need to further provide actuation since the intake valve means will be held in position by the difference in pressure between the cylinder pressure and the ambient pressure, which will be described further below. Accordingly, the actuating means may thus only need to provide a relatively short actuating pulse to arrange the intake valve means in position.
The present invention is based on the insight that by combining a check valve and an intake valve means, a simple valve arrangement is provided which is controlled such that only a desired amount of gas is provided into the cylinder of which the valve arrangement is provided to. Hereby, when the check valve is arranged in an open state, the intake valve means can be controlled for closing the intake side valve at a desired point in time. Accordingly, an advantage of the present invention is that the amount of gas provided into the cylinder, especially at low loads, can be controlled such that too much over-expansion is avoided. Hence, energy losses are reduced and the power efficiency of the cylinder which the valve arrangement is provided to is increased. Hereby, a variable Miller stroke of the cylinder is provided. Furthermore, another problem which is mitigated with the present invention is that excessive expansion is reduced. An excessive expansion cools the exhaust temperature which may create a problem for vehicle after treatment systems.
Moreover, another advantage of using the above check valve is that the need of valve actuating means for starting the vehicle is reduced, since the valve will be arranged in an open/closed position by means of the pressure it is exposed to.
Hence, the check valve provides for a “fail safe mode” when starting the engine at situations where otherwise an actuating means may fail to function. Hence, the check valve increases the reliability for start-up of the engine.
According to an example embodiment, the check valve may be a reed valve.
A reed valve should be understood as a specific type of check valve. The reed valve has at least one plate, or blade, which provides the valve in an open state when the plate/blade is exposed to pressure from a first side and in a closed state when the plate/blade is exposed to pressure from its other side. More specifically, the reed valve is normally, when not exposed to any pressure, in a closed state. When providing the reed valve at an intake side, the plate/blade of the reed valve is arranged to provide the reed valve in an open state when gas is provided into the cylinder and closed when gas is provided out from the cylinder.
An advantage of using a reed valve is that the reed valve can be positioned in an open state by means of a relatively low backpressure from the cylinder. This is advantageous since the backpressure in the cylinder generally generates pumping losses, i.e. energy losses. Accordingly, using a reed valve will thus further increase the energy efficiency of the cylinder arrangement. Furthermore, a reed valve is compact in its configuration which is an important aspect of cylinders since it can further reduce dead volumes in the cylinder. Another advantage is that a reed valve has a relatively low force of inertia which makes the opening/closing of the valve a fast process. Hence, the reed valve can quickly turn from an open state to a closed state, and vice versa.
According to an example embodiment, the valve arrangement may further comprise retracting means configured to position the intake valve means for opening the intake side port when a pressure in the cylinder is above a predetermined pressure threshold limit.
When the intake valve means has been positioned such that it closes the intake side port of the cylinder and the piston in the cylinder moves downward, the pressure in the cylinder will be reduced and the intake valve means will be kept in the closed position by means of the pressure difference between the pressure inside the cylinder and the pressure outside the cylinder. Hereby, the actuating means may be turned off since the difference in pressure will keep the intake valve cans in the closed position. However, when the piston in the cylinder moves upwards again, the pressure will increase and when the pressure is above a predetermined pressure threshold limit, the retracting means will position the intake valve means for opening the intake side port. It should however be readily understood that the increase in pressure will provide the check valve in the closed state, either before the intake valve is positioned in the open state or at the same time as the intake valve means is positioned in the open state. Accordingly, the intake valve means is automatically positioned in the open position when the pressure in the cylinder reaches the predetermined threshold limit.
Furthermore, the timing of when the intake valve means is positioned in the open state can be controlled by means of controlling the retracting means. If the retracting means is a spring, as will be described below, the timing can be controlled by means of the spring stiffness. Hence, the intake valve means can be arranged to be positioned in the open state before the pressure in the cylinder reaches the atmospheric pressure.
According to an example embodiment, the intake valve means may be a slide valve, wherein the actuating means is configured to slidingly position the slide valve for closing the intake side port. A slide valve is advantageous since it provides for a compact valve arrangement.
According to an example embodiment, the intake valve means may be a valve plate, wherein the actuating means is configured to tiltably position the valve plate for closing the intake side port. An advantage of having a tiltable valve plate is that the plate will be provided in the air stream of the cylinder and thus be provided to the closed position by means of the air flow. Hence, the demand on the actuating means is reduced.
According to an example embodiment, the retracting means may be a spring.
A spring is easily provided and may be arranged in many different forms. Also, a spring with suitable spring stiffness can be chosen such that the intake valve means is positioned in the open position when desired.
According to an example embodiment, the retracting means may be a torsion spring.
A torsion spring is particularly useful when having an intake valve means in the form of a valve plate which is configured to tiltably position the valve plate for closing the intake port. Hereby, the torsion spring will be an almost integrated apart in the valve plate, thus reducing of the overall size of the valve arrangement. Further, the torsion spring can also be adapted to tilt the valve plate to desired amounts. For example, the torsion spring can be chosen such that the valve plate is arranged in the open position by rotating the valve plate around the torsion spring by 90 degrees or 180 degrees as seen from the closed state. It can of course be opened to a lesser degree or to a larger degree as well if desired.
According to an example embodiment, the retracting means may be a coil spring. The retracting means may also be a pneumatic spring.
According to an example embodiment, the actuating means may be a pneumatic actuating means. A pneumatic actuating means is advantageous since it can provide a short pulse of pressurized gas that will force the intake valve means to be positioned such that the intake port is closed.
According to an example embodiment, the intake valve means may be a poppet valve actuated by means of the pneumatic actuating means. A poppet valve is advantageous to use when the actuating means is a pneumatic actuating means.
According to an example embodiment, the actuating means may be an electromagnetic actuating means. The electromagnetic actuating means may be a rotating electric motor or a linear electric motor, etc.
Other actuating means than those of the above description are of course also conceivable, such as e.g. a permanent magnet.
According to an example embodiment, the cylinder may comprise a cylinder relief through hole, which in conjunction with a recess arranged in the intake valve means provides fluid communication between an inside volume of the cylinder and a volume delimited by the intake valve means and the check valve when the intake valve means and the check valve are arranged for closing the intake side port.
When the piston of the cylinder is moving in the downward direction within the cylinder and the intake valve means is arranged in a closed state, the cylinder will be exposed to a negative pressure. This negative pressure will have its peak when the piston is in the bottom dead centre of the cylinder. Further, when the piston is at the bottom dead centre the check valve will be arranged in a closed position. Hereby, a relative large negative pressure is provided in the volume that is delimited by the check valve and the intake valve means, which will remain at approximately the same levels during the upward motion of the piston. An advantage with the cylinder relief through hole in conjunction with the recess in the valve means is that gas can be provided from the inside of the cylinder into the volume delimited by the check valve and the intake valve means, such that the negative pressure therein is reduced. The force of the retracting means can thus be reduced which provides for further flexibility in choosing retracting means.
According to an example embodiment, the check valve may comprise a check valve relief through hole for providing fluid communication between an inside volume of the cylinder and a volume delimited by the intake valve means and the check valve when the intake valve means and the check valve are arranged for closing the intake side port.
A further example of relief through hole is provided which allows gas from the cylinder to enter the volume delimited by the intake valve means and the check valve when the intake valve means and the check valve are arranged for closing the intake side port at all times when the check valve is in a closed state.
According to second aspect of the present invention there is provided a cylinder for an internal combustion engine arrangement, the cylinder comprising a check valve arranged at an intake side port of the cylinder for controlling gas flow into the cylinder, wherein the cylinder further comprises an intake valve means positioned upstream from the check valve, and an actuating means configured to controllably position the intake valve means for closing the intake side port.
According to an example embodiment, the cylinder may further comprise a second check valve arranged at an outlet side port of the cylinder for controlling gas flow out from the cylinder.
Hereby, a check valve is used as an intake valve as well as an outlet valve for the cylinder. The advantages of having a check valve at the outlet of the cylinder are analogous to those described above for the check valve at the inlet port.
According to an example embodiment, the cylinder may be a compression cylinder provided in a split-cycle internal combustion engine.
Further effects and features of the second aspect of the present invention are largely analogous to those described above in relation to the first aspect of the present invention.
According to a third aspect of the present invention there is provided an internal combustion engine arrangement comprising a cylinder according to any one of the above described example embodiments.
According to a fourth aspect of the present invention there is provided a vehicle comprising a cylinder according to any one of the above described example embodiments.
Effects and features of the third and fourth aspects of the present invention are largely analogous to those described above in relation to the first and second aspects of the present invention.